en_tn/job/06/16.md

which are darkened because of ice over them ... and because of the snow that hides itself in them

These two phrases have the same meaning. They describe how the streambed is full of ice and snow in the winter. Alternate translation: "which look dark in the winter because they are covered with ice and are full of melted snow" (See: rc://en/ta/man/jit/figs-parallelism and rc://en/ta/man/jit/figs-explicit)

because of the snow that hides itself in them

This speaks of the snow melting and the water going into the streambed as if the snow were hiding in the streambed. Alternate translation: "because the snow melts and goes into them" (See: rc://en/ta/man/jit/figs-personification)